UNIFIED SOIL CLASSIFICATION SYSTEM <br />UNIFIED SOIL CLASSIFICATION AND SYMBOL CHART <br />COARSE-GRAINED SOILS (more than 50% of material is larger than No. 200 sieve size.) <br />GRAVELS More than 50% of coarse fraction larger than No. 4 sieve size <br />SANDS 50% or more of coarse fraction smaller than No. 4 sieve size <br />Clean Gravels (Less than 5% fines) <br />GW <br />GP <br />Well-graded gravels, gravel-sand mixtures, little or no fines <br />Poorly-graded gravels, gravel-sand mixtures, little or no fines <br />Gravels with fines (More than 12% fines) <br />GM <br />GC <br />Silty gravels, gravel-sand-silt mixtures <br />Clayey gravels, gravel-sand-clay mixtures <br />Clean Sands (Less than 5% fines) <br />SW <br />SP <br />Well-graded sands, gravelly sands, little or no fines <br />Poorly graded sands, gravelly sands, little or no fines <br />Sands with fines More than 12% fines <br />SM Silty sands, sand-silt mixtures <br />SC Clayey sands, sand-clay mixtures <br />FINE-GRAINED SOILS (50% or more of material is smaller than No. 200 sieve size.) <br />SILTS <br />AND <br />CLAYS Liquid limit less than 50% <br />SILTS <br />AND <br />CLAYS Liquid limit 50% or greater <br />HIGHLY ORGANIC SOILS <br />ML <br />CL <br />OL <br />MH <br />CH <br />OH <br />PT <br />Inorganic silts and very fine sands, rock flour, silty of clayey fine sands or clayey silts with slight plasticity <br />Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays <br />Organic silts and organic silty clays of low plasticity <br />Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts <br />Inorganic clays of high plasticity, fat clays <br />Organic clays of medium to high plasticity, organic silts <br />Peat and other highly organic soils <br />GW <br />GP <br />GM <br />GC <br />SW <br />SP <br />SM <br />SC <br />LABORATORY CLASSIFICATION CRITERIA <br />cu D 50 D 30 = --greater than 4; Cc = between 1 and 3 D 10 010 x D50 <br />Not meeting all gradation requirements for GW <br />Atterberg limits below "A" Above "A" line with P.I. between line or P.I. less than 4 4 and 7 are borderline cases Atterberg limits above "A" requiring use of dual symbols line with P. I. greater than 7 <br />cu D 50 D 30 = --greater than 4; Cc = between 1 and 3 <br />D 10 01o xD60 <br />Not meeting all gradation requirements for GW <br />Atterberg limits below "A" Limits plotting in shaded zone line or P.I. less than 4 with P.I. between 4 and 7 are <br />Atterberg limits above "A" borderline cases requiring use line with P. I. greater than 7 of dual symbols. <br />Determine percentages of sand and gravel from grain-size curve. Depending on percentage of fines (fraction smaller than No. 200 sieve size), coarse-grained soils are classified as follows: Less than 5 percent .................................... GW, GP, SW, SP More than 12 percent .................................. GM, GC, SM, SC 5 to 12 percent ................... Borderline cases requiring dual symbols <br />PLASTICITY CHART <br />60 ,,/ � � 50 <br />� CH / / <br />>< 40 V" ALINE: Vp1 = on(LL-20) � 30 >-CL ,,/ MHloH 20 / j:: / 10 ...J CL+ML ./ ML&OL II.. 0 0 I 10 20 30 40 50 60 70 80 90 100 <br />LIQUID LIMIT (LL) (%)